Soak beans overnight in three times as much water as beans.
Peel onions.
Bring beans to the boil in a large pan with 3 litres of water, onions, sage and olive oil, and cook for 1½ hours.
Then add 1 tablespoon of salt and continue cooking until the beans are very soft, about 1 more hour. Add a bit more water as needed.
When the beans are done, strain them, saving the cooking water, and allow to cool.
Using a blender or a stick blender, briefly whizz 420g of the beans together with the tahini and lemon juice; small pieces should still be visible. Blend in a bit of cooking water as needed. Season to taste with salt.
Deseed the sivri/cayenne pepper and finely dice.
Toast the bread until dark brown. Spread the bean paste on plates.
Arrange the remaining beans and the diced sivri/cayenne on top, drizzle with olive oil and sprinkle with sumac. Serve with the bread.
